text: A simple way to monitor the change in viscosity, and thus, the extent of the reaction, in a curing process is to measure the variation of the elastic modulus.
  To measure the elastic modulus of a system during curing, a rheometer can be used. With dynamic mechanical analysis, the storage modulus (G) and the loss modulus (G) can be measured. The variation of G and G" in time can indicate the extent of the curing reaction.
  As shown in Figure 4, after an "induction time", G  and G"  start to increase, with an abrupt change in slope. At a certain point they cross each other; afterwards, the rates of G and G" decrease, and the moduli tend to a plateau. When they reach the plateau the reaction is concluded.
  When the system is liquid, the storage modulus is very low: the system behaves like a liquid. Then the reaction continues and the system starts to react more like a solid: the storage modulus increases.
  The degree of curing, , can be defined as follow:
  The degree of curing starts from zero (at the beginning of the reaction) and grows until one (the end of the reaction). The slope of the curve changes with time and has his maximum about at half of the reaction.